I. Field of the Invention
The present invention concerns a prosthetic joint implant having a tissue-integratable rough surface and as a special example a porous coating on a surface other than that which may be commonly provided for the intramedullary prosthetic-bone interface. The invention is for mitigation of latent wear debris dispersion following implantation.
II. Problems and Known Art
Artificial joint implants are known articles of manufacture, which can provide for remarkable remediation of painful and dysfunctional joints. In the known conventional practice of total joint replacement, the concave surface of an ultra high molecular weight polyethylene (UHMWPE) implant mates and articulates with the convex surface of a hard metallic or ceramic component. For example, in an enarthrodial joint such as the hip, a femoral component having a metal or ceramic ball is articulated in match with an UHMWPE acetabular cup.
The femoral component of a total conventional hip replacement generally has a metal stem which is inserted into and stabilizes the composite component within the medullary canal of the proximal femoral shaft, and the preferred total conventional hip replacement femoral component further has a collar at the upper end of the stem which rests upon the resected bone plane of the upper femur. Such component can be one adapted to be stabilized with a surgical cement such as polymethylmethacrylate where there typically is a more smooth but sometimes grooved stem surface for stem integration between it and the intramedullary bone (periprosthetic bone) and/or stabilized by ingrowth of bone from the implant-bone interface, in which case a porous coating is known to cover that part of the stem to be in contact with the periprosthetic bone. See, e.g., BioPro, Inc., xe2x80x9cPSL Total Hip Replacement System,xe2x80x9d 1991. Although they are adapted for particular bodily joints, many other body joint implants are broadly analogous to the hip in such considerations.
Although UHMWPE has been proven to be exceptionally durable, this material is, nonetheless, vulnerable to an unfavorably high rate of wear that certain researchers and practitioners note results in periprosthetic bone dissolution and premature failure of the procedure, which may be seen more disastrously in the hip. For the most common total joint coupling in current use, i.e., cobalt-chrome alloy on UHMWPE, the polyethylene wear rate is typically on the order of 0.1 to 0.3 mm annually, which results in the proliferation of billions of wear particles per year. Over the subsequent years, the massive over-loaded accumulation of particulate wear debris, including a substantial portion of submicron sized particles, gains access to the bone-prosthetic interface and induces an adverse foreign body reaction associated with phagocytic activity and the attendant release of bone-resorptive chemical mediators (periprosthetic osteolysis). Structural bone loss due to debris-induced periprosthetic osteolysis is now commonly cited as a major etiological factor in implant loosening and failure of joint replacement procedures. See, e.g., Jacobs, Soc. Biomaterials Trans., April 1998, p. XLVII. See also, Goodman, Id., p. XLVIII; Ramamurti et al., Id., p. 5; Goodman et al., Id., p. 58; Clineff et al., Id., p. 445; Amstutz et al., Id., p. 447. But see, Townley, Ceramic Trans., Vol. 48, pp. 23-34, 1995 (structure of implant to physiologically stress loading remaining bone stock may play part in ameliorating or precluding initial loosening to hinder or preclude osteolysis).
It would be desirable to ameliorate if not overcome such a problem. It would be desirable to fulfill such a longstanding lack and long felt need in the art.
The invention provides a prosthetic component comprising an artificial joint implant component having an extramedullary, non-bone-interfacing, soft fibrous tissue-integratable rough surface. One or more components may make up a prosthesis.
The invention is useful in arthroplasty.
Significantly, when the prosthesis is implanted, the exposed out of bone rough surface has been shown to routinely engender ingrowth of soft fibrous tissue so that it forms, as it were, a capsular xe2x80x9cbagxe2x80x9d in which wear debris from the joint is trapped, thus keeping those particles from gaining access to the bone-prosthetic interface. And so, with mitigation of wear debris dispersion to the periprosthetic bone, the problem in the art of debris wear-induced osteolysis can be ameliorated, if not overcome, and the longstanding lack and long felt need in the art are addressed if not overcome and fulfilled.